Note about attachment paths: Attachments may have embedded /
characters that are sent unescaped to CouchDB. You can use this to
provide a subtree of attachments under a document. A DocID must have
any / escaped as %2F. So if you have document a/b/c with an
attachment d/e/f.txt, you would be able to access it at
http://couchdb/db/a%2fb%2fc/d/e/f.txt.